The Taipei MetroXinbeitou Branch Line is an elevated, high-capacity branch line of the Tamsui Line. It first opened for service on March 28, 1997. The line is 1.2 km (0.75 mi)-long and consists of two stations.
The origins for the line can be traced as far back as 1916, where its predecessor line of a similar route was built and operated by the Taiwan Railway Administration (also called the Xinbeitou Line). It was last operated on July 15, 1988 by diesel units before ceasing service for construction of the metro line. On March 28, 1997, the line re-opened for service as part of the Taipei Metro.
The operation of the line has been problematic since its opening. Complaints of noise pollution by residents along the line have led to severe restrictions. Barely six months after the line's opening, train frequency had to be reduced. On November 1, 1998, the number of cars operating on the line was reduced from six to three. Up until 2007, the operating hours were limited to between 7 am and 9 pm only. Trains currently still operate with a speed limit of 25 km/h (16 mph) due to flange on the line's sharp curves.
TRTS completed the installation of the sound-proofing barrier along the line by 2006, and on September 14, 2007 extended its operating hours to between 6 am and midnight. It was hoped that if the noise standards were deemed to be at an acceptable level that the current Orange Line trains on the Tamsui Line could operate on the Xinbeitou Line instead. Trains operate at a maximum headway of one per 7–8 minutes during peak hours.
It has been reported that the line is operating at a loss. A proposal was put forth in 2005 that a maglev train operation would solve the problem of noise pollution, but its feasibility on operating costs became a subject of ridicule.
3-car C301 trains, which operated on the line up until 2007.
A modified C301 (trainset 013/014) originally operated on the line in a 3-car formation, making it unique on the system. From 2007 onwards, the train was replaced by a purpose-built C371 of a similar length.